Sound-shielding housing for a microphone



Oct. 7, 1958 4 A. L. D] MATTlA 2,855,067

SOUND-SHIELDING HOUSING FOR A MICROPHONE Filed April 29, 1955 INVENTOR ATTORN S United States Patent SOUND-SHIELDING HOUSING FOR A MICROPHONE Alfred L. Di Mattia, Fairfield, Conn., assignor to Dictaphone Corporation, Bridgeport, Conn., a corporation of New York Application April 29, 1955, Serial No. 504,902

18 Claims. (Cl. ISL-34) This invention relates to a microphone housing which permits a user to speak into a microphone without disturbing nearby listeners and which, conversely, prevents sound other than the users voice from reaching the microphone.

An object of the present invention is to provide such a microphone housing which is light and compact but yet very efficient in its sound shielding action.

Another object is to provide such a housing which is very easy to use even for long periods of time.

A further object is to provide an inexpensive microphone housing having the above characteristics.

Although microphone housings of one kind or another intended for this purpose have been known for many years, until recently none has attained any real measure of commercial success. Undoubtedly a reason for this has been the difficulty of satisfying in a reasonable size housing the inter-related requirements of good soundshielding and easy breathing for a user. It is desirable for good sound-shielding that the user enclose his mouth and nose in the housing when he is speaking but it is very inconvenient for him to have to remove the housing from his face for each breath. Not only does this interfere with his speaking but, since it requiresa continuous and conscious effort, after a time it becomes very tiring. Therefore an adequate air passage through the housing must be provided to permit normal breathing and thus to enable the user to speak without distraction.

Some microphone housings in the past permitted easy breathing through them but gave very unsatisfactory sound-shielding while others provided excellent soundshielding but almost entirely prevented breathing. Generally speaking, except for the housing described and claimed in co-pending application Serial No. 215,770, filed March 15, 1951, now Patent No. 2,769,040, there has been no satisfactory arrangement which avoids these two extremes.

In designing a microphone housing of the kind in question it is necessary to provide a breathing passage through the housing large enough to enable a user to breathe without effort while holding the housing to his face. The pressure required for a user to force a requisite amount of air through the housing in breathing, i. e. the back pressure, is related to the ratio of the length of the air passage through the housing to its effective airconducting area. For a given minimum back pressure, the longer the passage, the larger its effective area must be.

It is evident though, if one also considers the companion requirement for good sound-shielding, that the passage through the housing cannot be simply a straight tube of sufficient size, possibly lined along its inside with sound absorbing material, because such a tube does not give sufficient attenuation of the users voice and this destroys the intended usefulness of the housing.

Apart from these considerations of easy breathing and good sound-shielding for such a microphone housing are the equally important factors of size and weight. It

goes without saying that if size and Weight were unimportant it would be relatively easy to make a large housing which satisfies the other requirements. But where portability and convenience of use are prime factors, as in any such device which is to have wide market attraction, obvious expedience which neglect size and weight must be discarded in favor of an arrangement which provides a light and compact construction. Preferably, a microphone housing should be not greatly larger than the microphone itself and it should be so light in weight that any user will be able to hold it without conscious effort. The present invention, it is believed, has achieved a unique fulfillment of each of these requirements with each very nearly being satisfied as though it were the only one necessary to consider.

In accordance with the present invention, in one specific embodiment thereof, a hollow thin walled cylindrical container having a length and diameter each of approximately four inches and having relatively large air passages therethrough each approximately one inch in diameter is used to provide a highly effective soundshielding microphone housing. Even though no sound absorbing material whatever need be used in this housing, its sound-shielding eifect is approximately the same as the housing shown in the above-identified co-pending application. The structure of the-present housing, is nonetheless very simple and inexpensive.

A better understanding of the present invention together with a fuller appreciation of its many advantages will best be gained from the following description given in connection with the accompanying drawings in which:

Figure 1 is a front perspective view of a microphone housing embodying features of the present invention; and

Figure 2 is an enlarged side view, partially in crosssection, of the same housing.

The housing, generally indicated at 10, shown in these drawings includes a hollow, thin walled container 12 to which is joined a triple purpose handle 14, which at the same time serves as a very convenient hand grip for the housing, as a passage for the users breath into and out of the housing, and as a conduit for microphone and control wires. The housing 10 also includes a flexible face seal 16 of resilient material such as rubber or the like attached around one end of container 12 and adapted to enclose the mouth and nose of the user. Positioned within the open end of container 12, is a microphone 18 which is preferably placed relative to seal 16 so that it will be just in front of the mouth of a user when he holds housing 10 so that the seal 16 is pressed against his face.

With the microphone so placed, almost all of the sound in the users voice is applied directly to the microphone so only a relatively small amount of the sound reflected from the housing microphone thus minimizing distortions caused by such reflected sound waves.

Led out the bottom of handle 14 is a microphone and control lead cable 20 which runs to a suitable dictating machine or other voice recorder such as shown in the above-mentioned co-pending application. Handle 14 carries an on-off switch 22 which controls this dictating machine.

As seen in Figure 2, the inside of container 12 is partitioned into an open ended space 24 around the microphone 18 and a substantially closed space 25 by means of a vertical wall 28 and a horizontal tube 30. Wall 28 is in the form of an annular disk and has a central opening 29. This wall supports tube 30 at one end in cantilever fashion, the passage through this tube being the same size as and centered relative to opening 29. Tube 30 extends within space 25 from Wall 28 almost but not quite to the rear wall 32 of the container 12.

Supported a short distance in 'front of opening 29 in wall 21% by any suitable means such as mounting posts 34 is microphone 18. This microphone is made to have a diameter somewhat greater than the diameter of opening 29 so that, in addition to its function as a microphone, it also acts as a sound baffle. The sound of a users voice, therefore, will be deflected out of a straight line path before entering tube 30 via opening 29.

Sound waves after entering tube 3% pass along the tube to its far end whereupon they are deflected outward and redirected backward by means of wall 32 into space 25. However, the only escape for these waves from space 25 is an opening 36 through the side wall of container 12 and so, much of their power is lost in bouncing back and forth between walls 32 and 28.

Those sound waves which do manage to enter opening 36 then must pass along a tube-like passage 37, centered relative to opening 36 and running the length of handle 14, before they reach the outside. When they finally escape they are not loud enough to disturb even a nearby listener, if indeed they can be heard at all.

in this structure, it is possible to make the various openings and passages large enough easily to pass the amount of air needed by a user in normal breathing without adverse efiect on the sound-shielding action of the housing. The fact that the users breath is expelled downward through passage 37 is of particular advantage when this housing must be used in crowded places. Moreover, since no sound absorbing material is used in this construction, little if any, moisture or odor will be trapped within the housing.

The following structural dimensions have been found satisfactory in an embodiment of this housing which has been built and tested and found highly effective: inside diameter of container R2, 3%"; wall thickness of container 12, /8; inside distance between wall 28 and wall 32, 2 distance between end of tube 30 and wall 32, 7 distance between the back of microphone 18 and the front of wall 2%, Mi; outside diameter of microphone 13, 1%; inside diameter of tube 30 and opening 29 in wall 28, 1''; outside length of container 12 from the front of seal 16 to the rear of wall 32, 3%"; thickness of walls 28, 32 and tube 31 /s"; inside diameter of passage 37 and opening 36, 1"; length of handle 14, Opening 36 was approximately centered between walls 28 and 32. Cellulose acetate butyrate is suggested as one suitable material for the above parts although other materials may be equally satisfactory.

The above description is intended in illustration and not in limitation. Various changes and modifications in the structure described may occur to those skilled in the art and these can be made without departing from the spirit or scope of the invention as set forth.

l claim:

1. A microphone housing comprising, a container with an open end and having walls enclosing a relatively large space; a flexible face seal fitted around the open end of said container and adapted to enclose the mouth and nose of a user; an elongated tube-like member extending away from the open end of said container into said space and supported therein in cantilever fashion by a first wall bounding said space, the first end of said member extending almost to a second Wall bounding said space; microphone means supported adjacent the second end of said member for forming a battle or obstacle in front of the passage through said member; and means forming an elongated tube-like passage from said relatively large space to the ouside, said elongated passage extending approximately at right angles to the passage through said tube-like member.

2. The combination of elements as in claim 1 in which said means forming an elongated tube-like passage also serves as a handle by which a user can hold said housing.

3. A microphone housing comprising: a short tube-like member; container means enclosing all but one end of said member in a hollow space of substantially greater volume than the volume of the enclosed part of said member; means forming a passage running from said hollow space to the outside in a direction generally perpendicular to the axis of said tube-like member; and means for mounting a microphone adjacent the unenclosed end of said member.

4. The combination of elements as in claim 3 in which said means enclosing said tube-like member includes a flat extended surface positioned closely in front of the enclosed end of said member and in which the enclosed part of said tube-like member is approximately centered Within said hollow space.

5. The combination of elements as in claim 4 in which said microphone is positioned closely in front of the unenclosed end of said tube-like member and serves as a bafiie to sound entering the opening in said member.

6. The combination of elements as in claim 3 in further combination With a face enclosing seal fitted around the unenclosed end of said tube-like member and said microphone, said face seal being adapted to enclose the mouth and nose of a person when he speaks into said microphone.

7. In a microphone housing, a container open at one end and having sound impervious walls including a rear wall, a dividing wall partitioning the inside of said container into a first substantially enclosed space and a secand open-ended space, said dividing wall having a central opening in it, a short length tube extending from the opening in said dividing wall almost but not quite to said rear wall, said rear wall being approximately at right angles to the passage through said tube, the crosssectional area of said tube being substantially smaller than the cross-sectional area of said container, the passage through said tube being aligned with said central opening and being approximately centered within said first space, the wall of said tube being relatively sound impervious, tubular means forming an air passage from said first space to the outside, said air passage being connected to said first space by an opening lying generally at right angles to the passage through said tube; and means for mounting a microphone in said second open-ended space.

8. The combination of elements as in claim 7 in which said tubular means forming an air passage is a handle attached to said container and extending downward, this handle having a tube-like passage through it.

9. In a microphone housing, means forming an openended space into which a user can speak, means for mounting a microphone in said open ended space and adjacent the users mouth, wall means including a rear bounding wall and forming a substantially enclosed space within said housing, means forming a short tube-like air passage from said open space and extending into said en closed space, said air passage extending almost but not quite to said rear bounding wall, and means forming a second air passage extending from said enclosed space to the outside and including an exit opening from said enclosed space which lies generally at an angle to said rear bounding wall, said exit opening and said air passage being approximately equal in size.

10. In a microphone housing, an open ended container having a cylindrical side wall and a rear wal an annular flat disk dividing said container into a substantially enclosed space and an open ended space; a short tube supported in cantilever fashion by said disk and extending from said open-ended space back through said substantially enclosed space almost but not quite to said rear wall; and tubular means forming an air passage from said substantially enclosed space to the outside and including an opening through said cylindrical side wall approximately centered between said disk and said rear wall, said opening being approximately equal in size to the opening through said short tube.

11. The combination of elements as in claim 10 in further combination with baffle means forming a sound obstruction in said open ended space in front of said short tube.

12. The combination of elements as in claim 11 in which said tubular means forming an air passage is a hollow handle attached to said container.

13. The combination of elements as in claim 11 in which said baffle means includes a microphone.

14. The combination of elements as in claim 11 in further combination with a flexible seal around the open end of said container and adapted to enclose the mouth and nose of a user.

15. The combination of elements as in claim 14 in which the walls of said container and said tube are sound impervious and the openings and passages through said housing are just large enough to permit the user to breathe freely while holding said housing to his face.

16. A microphone housing comprising: a short tubular member of small volume, container means enclosing all but one end of said member in a very large hollow space of about nine times the volume of said tubular member, means forming an elongated passage running from said hollow space to the outside from a point other than at the enclosed end of said tubular member, and means for mounting a microphone adjacent the unenclosed end of said member.

17. A microphone housing comprising a cylindrical body closed at one end by a rear wall and having an inside length of roughly 4 inches and an inside diameter of roughly 4 inches, an annular disk spaced roughly 2 inches from the rear wall and dividing the inside of said container into a closed space and an open space, the opening in said'disk being of the order of 1 inch in diameter,-

a short length tube supported by said disk and projecting into said closed space to within roughly A1 inch of said rear wall, the inside opening of said tube being roughly 1 inch in diameter and being centered relative to the opening in said disk, a microphone positioned in said open space in front of the opening in said disk, and a handle projecting at approximately right angles from the side of said body, said handle having a tubular passage therethrough connecting, by an opening through the side of said body, said closed space and the outside air, the diameter of said tubular passage being roughly 1 inch and its length roughly 5 inches.

18. in a sound shielding microphone housing wherein the nose and mouth of a person using the housing are enciosed therein and where it is desirable for the person to breathe without effort while the housing is continuously held to his face for long periods of time, a hollow, thin-wal1ed container having an open end and a flat rear wall and surrounding a large volume, a face shield attached around the open end of said container and adapted to enclose the nose and mouth of a person, an annular partition having a central opening and positioned within said container slightly inward from the open end thereof to enclose a space therewithin, a small-diameter shortlength thin-walled tube supported by said partition and extending within said enclosed space from the opening in said bafiie almost to said rear wall of said container, the space within said tube being very much smaller than the enclosed space within said container formed by the walls thereof and said partition, the diameter of said tube being large enough to permit a person to breathe through it easily, the length of said tube being longer than its diameter, an elongated air passage extending from an exit opening in said container from said enclosed space to the outside air, said exit opening and said air passage lying approximately at right angles to said tube, the diameter of said air passage being roughly the same as that of said tube, the length of said passage being substantially greater than that of said tube, and a microphone positioned as a bafiie closely in front of the opening in said partition.

References Cited in the file of this patent UNITED STATES PATENTS 733,330 New July 7, 1903 1,700,553 Swan Jan. 29, 1929 1,909,375 Muller May 16, 1933 2,508,581 Morrow May 23, 1950 2,667,940 Gallihugh Feb. 2, 1954 FOREIGN PATENTS 549,518 Great Britain Nov. 25, 1942 13,302 Australia July 2, 1934 of 1933 

